Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
h,w=map(int,input().split())
grid=[list(input()) for i in range(h)]

sum=0
for i in range(h):
  for j in range(w):
    if grid[i][j]=='.':
      sum+=1   

grid[0][0]=0
loc=[[0,0]]      
    
ans=0
for k in range(1,h*w):
  next_loc=[]
  for [y,x] in loc:
    for [i,j] in ([1,0],[-1,0],[0,1],[0,-1]):
      if 0<=y+i<=h-1 and 0<=x+j<=w-1:
        if grid[y+i][x+j]=='.':
          grid[y+i][x+j]=k
          next_loc.append([y+i,x+j])
    loc=next_loc
  if [h-1,w-1] in loc:
    ans=k
    break

if ans==0:
  print(-1)
else:
  print(sum-k-1)